Sapphire is widely used for screen or protective panel of cell phone, laptop, watch, etc. due to its good physical and chemical properties and light transmittance. However, such application requires good flatness and therefore, has a high requirement for the flatness during the processing of sapphire panel. Usually, a grinding disc is needed in the process, together with slurry, for polishing.
Currently, the polishing disc is a metal disc, an alloy disc or a composite disc provided with coarse grinding grooves, the grinding groove cooperating with slurry for grinding and polishing sapphire. Disc containing copper is the best polishing disc for polishing sapphire. For example, a Chinese utility model patent with a publication number CN202174508U discloses a synthetic copper grinding disc, which is provided with several undulated grooves, the grooves being annular areas. However, the following problem exists when a double-face polisher to polish a sapphire panel. During the processing, referring to FIG. 1, the sapphire panel is placed within a mold cavity 5 of a planetary gear 3 that is located on a lower disc and forms planet trains by engaging with an inner gear ring 2 and a sun gear 4, respectively. The above utility model realizes single-face polishing of sapphire panel by rotation of a disc containing copper on one side, or double-face polishing of sapphire panel by the rotation in opposite directions of the upper and lower discs. The planetary gear 3 performs rotation and revolution via transmission of the planet trains so as to enhance the polishing effect. Currently, conventional sapphire panel is used for screen of cell phone and laptop, and is usually in a square shape as shown in FIG. 1. In the process that the sapphire panel placed on the planetary gear follows the rotation and revolution of the planetary gear, the shadow areas on the outer side and the inner side of the annular areas of the grinding grooves on the disc containing copper as shown in FIG. 1 is an intermittent grinding and polishing area where the edges and corners of the sapphire panel enters, and the middle position is a normal grinding and polishing area. After a period of polishing, as the hardness of sapphire is relatively high, the above two areas of the disc containing copper will have abrasion to different extent, which causes change in the flatness of the disc containing copper and makes the middle area lower than the circumferential areas. The error in the flatness of the grinding disc will directly lead to reduction of the flatness of the sapphire panels in the contact processing between the sapphire face and the grinding disc face. Severer, under the force applied by the upper polishing disc containing copper, the workpiece may be broken.
Therefore, a sapphire polishing disc containing copper needs to be researched and developed in this field, which will not generate uneven abrasion.
In addition, due to the high hardness of sapphire and the soft texture of copper, though copper grinding disc well performs the function of grinding sapphire, the grooves on the surface of the disc containing copper for grinding sapphire are easy to be worn flat by sapphire. Therefore, after a period of processing, the grinding grooves of the disc containing copper need to be repaired to enhance the sharpness to increase the processing efficiency. In order to repair conventional discs containing copper, at least one of the upper and lower discs that rotate in opposite directions needs to be removed from the polishing machine and be repaired by a special repairing machine. The labor intensity is rather high, and the works takes long labor hours, severely affecting the productivity of the manufacturing firm.
Therefore, a method for repairing discs containing copper facing each other for polishing sapphire which is more concise and convenient needs to be provided.